Method for making products from plastic material



Nov.. 15, 1932.

F. w. HARNEY METHOD FOR MAKING PRODUCTS FROM PLASTIC MATERIAL OriginalFiled March 11, 1951 I (NVENTOR 'nuzczs 14/ [/arnc BY 423/1 TTORNEYPatented my. 15, 1932 UNITED STATES PATENT OFFICE.

FRANCIS w. HABNEY, OI LOOKPOBT, NEW YORK, ASSIGNOR TO THE UPSON COMPANY,OF LOCKPOBT, NEW YORK, A CORPORATION OF NEW YORK KE'IHOD FOR MAKINGPRODUCTS FROM PLASTIC MATERIAL I Original application filed larch 11,1931, Serial No. 521,772. Divided and this application filed Kay 8,1932. Serial No. 609,640.

This invention relates to a method of making articles from lasticmaterial, such for exam le as the ma ing of wallboard from a plasticmass placed between two liner sheets and hardened to form an intumescentporous cellular body. 7

An object of the invention is the provision of a generally improvedmethod which is more satisfactory than those previously known, for themaking of such materials.

Another object of the invention is the provision of a method which isarticularly satisfactory in the making of relatively wide pieces orstrips of material.

Still another object is the provision of a method especially adapted forthe manufacture of wallboard by a substantially continuous process, bywhich method satisfactory wallboard may be made of relatively greatwidth.

To these and other ends the invention resides in certain improvementsand combinations of parts, all as will be hereinafter more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

In the drawin Fig. 1 is a iagrammatic cross section through a wallboardat an intermediate stage of its manufacture according to the present,

method, and

Fig. 2 is a diagrammatic cross section through the same board after ithas been completed.

The same reference numerals throughout the several views indicate thesame parts.

This application is a division of my application for apparatus formaking roducts from plastic material, Serial No. 521, 72, filed March11, 1931. The present case is intended to claim the method disclosed insaid prior application, while the claims of the prior application willbe limited to the machine for carrying out the method, the machine beingfully disclosed in said prior application.

The method of the present invention relates to the manufacture ofvarious articles from plastic material and will be described withparticular reference to the manufacture of wallboard, although it is tobe understood that other articles or products in addition to wallboardmay also be made.

According to the present method, plastic material is placed as a fillingor core between two liner sheets, and the composite structure of fillingand liner sheets is then subjected to heat. Plastic fillings of a. kindsuitable in this connection ordinarily contain vaporizable substances,such as moisture which will form steam upon heating.

The formation of the vapor during the step of heating creates internalpressures in the product which tend to distort it by forcing the linersheets away from each other, splitting .the core or filling. In someinstances, and especially when the product is being made in relativelynarrow widths such as four feet, for example, the internal pressuresformed in this way are found to be not greatly detrimental, and can becontrolled to a sufficient extent, as for example by confinin thematerial between platens during part 0 the heating operation. I

When the material is made in relatively great widths, such for exampleas widths of eight feet, it is found that there is a considerabletendency for the liners to be distorted or forced away from each other,and the distorting tendency is so great that it cannot be satisfactorilycontrolled by the methods which have heretofore been used in making anarrow roduct. Even if latens are used to confine t e product duringeating, the liners will be forced away from each other to some extentafter the product emerges from the platens (unless the platens are ofexcessive and uneconomical size or length), so that the resultingproduct is imperfect and in many cases entirely useless.

' The exact cause of this phenomenon in the manufacture of a wideproduct is not known with certainty, although it seems probable that itisdue to the internal pressure developed by vaporization of moisture inthe plastic filing. It also seems probable that the reason this is somuch more pronounced in the case of a wide product than in the case of anarrow product, is that the vapor causing the pressure can escape onlywith considerably more difiiculty, be-

cause it must force its way through a much greater distance of plasticmaterial from a point near the center of the product to the exposed edgethereof than when the material is substantially narrower. At any rate,whatever the exact cause may be it is a fact that in actual use. theliners are forced apart after leaving the platens and a considerableroportion of the product is spoiled when it is attempted to produce arelatively wide product at economical speeds. k

According to the method of the present invention, this unsatisfactorycondition of the product is ob ed and a satisfactor product is producedeconomically notwit standing the relatively great width thereof. Thepresent method contemplates the provision of one or more expansionchambers or cavities in the filling at intermediate points in the widthof the product. Whenonly one 'such cavity is used, it is preferablysubstantially at the center of the product in a transverse direction.This expansion chamber or cavity may be formed, for example, bypreventing or blocking off the suppl of plastic filli' to thespaceibetween the finer sheets at a esired intermediate point in thewidth of the product, so that no filling or at least less than thenormal amount of filling is deposited between the liners at the desiredintermediate point. This is illustrated in Fig. 1 of the accompanyingdrawing, showing an u per liner sheet 10, a lower liner sheet 11, a pastic more 12, and a cavity 13 in the su tially at the center of thesheet in a transverse direction. A

It is found that when this cavity is provided, accordin to the presentinvention, the above descri d distortion or splitting of the productdoes not occur. The exact reasons for this improved result are not knownwith certainty, but it seems robable that the ex ansion cavity 13 provies a chamber into w ich the vapor under pressure can flow to someextent, and from which it can escape through the somewhat porous linersheets more readily than at points where the filling is in close contactwith the liner sheets.

Furthermore, the cavity forms an expansion chamber into which some ofthe filling may e and durin the heating operation.

atever t e exact reasons for the imis found to be completely filled upby expansion of filling thereinto, so that there is no cavity presentwhich might form any defect inthe product.

Preferably the filling employed according commercial spec s..Furthermore, when the heat treatment is finished, the cavity originallyleft in the filling to the present invention not only is plastic, butalso is intumescent. For example, it may comprise a mixture of sodiumsilicate and a finely ground inorganic filler such as limestone ordolomite. buch a mixture is initially introduced between the linersheets when it is of a somewhat dough-like consistency. Subsequentheating of the product causes this mixture to intumesce so that itbecomes porous or filled with a multitude of relatively small cells,somewhat comparable in size and appearance to the cells of a loaf ofbread. Continued heating hardens and sets the product so that it finallybecomes rigid, strong, and water resistant, havin a hardness comparableto that of stone. ig. 2 illustrates a cross section through the productafter the heat treatment thereof is finished, and illustratesdiagrammatically not only the cellular nature of the filling or corewhen com leted, but also shows, by comparison with ig. 1, that theintumescentfilling expands so that the core of the final product issubstantially thicker than the layer of filling originally introducedbetween the liners. Fig. 2 also showsthat the expansion cavity 13disappears substantially completely during the intumescing operationbyflow of part of the filling thereinto.

By usin the method of the present invention, wall oard havm paperlinersand an intumescing filling 0 sodium silicate and ground limestonehas been satisfactorily constructed in widths as great as eight feetwhereas without the use .of the resent metho the attempt to produce wallcard of these materials in this width was frequently unsuccessful andresulted in a considerable proportion of board which became deformedafter emerging from the platens. When a product is made according toprior methods, without using the expansion cavity of the resentinvention, it is found that a strip of wallboard eight feet wide isfrequently as much as fifty or sixty thousandths of an inch thicker nearthe center of the board than near the edges thereof, notwithstanding thefact that the filling material was originally distributed uniformlybetween the liners. A variation in thickness or caliper of thismagnitude is often a serious defect. When the expansion cavity of thepresent invention is employed, however, it is found that the variationin caliper between the center and edges of an eight foot board does notexceed about ten or twelve thousandths of an inch, which is a great reorsixty thousandths. Also, when using the present invention the frictionalresistance to moving the board through .the platens is found to bematerially less than previously, the board .runs through'the platensmore smoothly, and the cellular structure of the board is greatlyimproved, the cells being duction from theprevious variation of fiftysmaller and more uniformly distributed, and the board being considerablystronger than similar boards made without the use of the presentinvention. 7

While the linersheets, es ecially in the case of wallboard, are prefera1y permanent- 1y retained on the filling or core, this is not essentialunder all circumstances and it is contemplated that the invention may beused also in making a'product which in its final form has no or onlyoneliner sheet. Hence the words liner sheet and liner as used in thisspecification and in the accom anying claims are intended to include anys eet material used on either side of the filling,"

at ot whether such use is permanent or temporary. For example, if theliners are to remam permanently attached to the filling, they may be ofheavy paper, cloth, or other suitable material. If one or both linersare to be later removed from the filling, one or both of. them may beformed from paper which is waxed or oiled to prevent it from sticklngpermanently to the filling, or of a str1 or piece of metal which isgreased or oiled kewise to prevent it from sticking permanently, andsuch liners may be stripped from the filling or core after emerging fromthe platens.

In carrying out the present method, theliners are preferably led overand between forming rolls, and the plastic filling is supplied by ahopper and introduced between the liners as they pass between the forminrolls, in the general manner disclosed in pson Patent No. 1,854,872,granted A ril 19, 1932. Supply of 'plastic material to t e space betweenthe liners is wholly or partially blocked oil at one or moreintermediate points in the width of the product. The liners are movedpreferably continuously through the forming rolls and then betweenheated platens or the like, to heat the plastic filling and cause intumescence thereof. Thus the product may be produced continuously, andthe continuous strip may or sizes as desired.

While one embodiment of the invention has been disclosed, it is to beunderstood that the inventive idea may be carried out in a number ofways. This application is therefore not to be limited to the precisedetails described, but is intended to cover all variations andmodifications thereof falling within the spirit of the invention or thescope providing of the appended claims.

I claim:

1. The method of making material comprising liner sheets and anintumescent filling between the liner sheets, which comprisesintroducing an intumescent filling into a part only of the space betweenlinersheets, a pressure-relievingcavity at an intermed ate point insuchspace,

be cut up into suitable lengths and Sllb".

jecting the liner sheets and filling to heat to cause said filling tointumesce.

2. The method of making wallboard which comprises introducing anintumescent filling into a part only of the space between two liner seets, providing a pressure-relieving cavity at an intermediate point insuch space, and subjecting the liner sheets and filling to heat to causesaid filling to intumesce. I

' 3. The method of making wallboard which comprises placing anintumescent fillin between two liner sheets, less quantity 0 filling perunit of surface area of the wallboard bemglplac'ed at one intermediatepoint-than er points, and subjecting the filling to heat to cause it tointumesce, so that the filling will tend to flow partially toward thepoint where less filling was placed.

4. The method of making wallboard which comprises introducin apredetermined thickness of intumescent ling between two moving linersheets throughout certain portions inorganic material between said linersheets at one point in their paths of travel in such manner that apressure-relievin cavity is provided at a point inwardly of t e edges ofsaid sheets, and subsequently confinin said liner sheets and fillingbetween heated p atens at another point in their paths of travel tocause said filling to intumesce, pressure caused thereby being partiallyrelieved by flow of filler toward said cavity.

(i The method of making products from plastic material which comprisesbringing two liner sheets into proximity to each other with a spacebetween them,'inserting a plastic filling in said space throughout themajor portion of the width of the assembled sheets while substantiallyexcluding filling from said space at an intermediate point in the widthof the sheets, and subjecting said filling and sheets to heat.

7. The method of making products from plastic material which comprisesbringing two liner sheets into proximity to each other with a spacebetween them, causing plastic filling to flow into said space throughoutthe major portion ofthe width of the assembled sheets whilesubstantially blocking oif flow of filling into said space at oneor moreintermediate points in the width of the sheets to provideone or morepressure-relieving 4- mew/s9 cavities, and subjecting said filling andsheets to heat.

8. The method of making products from plastic material which comprisesmoving two strips of sheet material substantially continuously betweentwo spaced rolls, inserting plastic material between said stripssubstantially as the pass between saidrollers and throughout t e majorportion of the width of 10 said strips while omitting lastic material ata predetermined point in t e width of said strips to create apressure-relieving cavity in the plastic material running longitudinallyof the strips at an, intermediate point in the width thereof, andsubjecting said strips and filling to heat.

9. The continuous method of making a product from plastic material whichcomprises moving two strips of sheet material 4 substantiallycontinuously between two spaced rollers, inserting plastic materialbetween said strips substantially as they pass between said rollers andthroughout the major portion .of the width of said strips whilesubstantially omitting plastic material at a predetermined point in thewidth of said strips to create a pressure-relieving cavity in theplastic material running longitudinally of the strips at an intermedlatepoint in the width thereof, and moving said strips and fillingsubstantially continuously to and betweien heated platens to confine andheat sai 10. The method of making wallboard which comprises moving twostri s of sheet material substantially continuous y between two spacedrollers, insertin an intumescent plastic filling between sai stripssubstantially as they pass betweensaid rollers and throughout the majorportion of the width of said strips while omitting said filling at apredetermined point in the width of said strips to create apressure-relieving cavity in the filling rumiing longitudinally of thestrips at an intermediate point in the width thereof, and moving saidfilled strips substantially continuously between heated platens. FRANCISW. HARNEY.

